1. Field of the Invention
The present invention relates to bicycle brake adjustment tools and procedures useful in properly setting the pads of cantilever, center pull or side pull caliper style brakes relative to the adjacent wheel of a bicycle.
2. Description of the Prior Art
The most commonly used brakes on bicycles today are caliper brakes which are essentially grouped into three basic category styles including cantilever, center pull and side pull, all of which may be adjusted with the present invention. Caliper brakes are hand actuated from hand levers mounted on the handlebars and connecting with cables which extend downward to pivotally mounted brake arms attached to a stationary frame member and supporting rubbery brake pads having a braking surface facing the side of the wheel. The braking surface of the pads is sufficiently close to the wheel that squeezing of the hand lever draws the cable upward to pivot the end of the brake arms inward about a mounting pivot to have the braking surface of the pads frictionally contact the wheel. Caliper brakes include two brake pads, one on either side of the wheel oppositely disposed from one another and functional in pairs or sets, and with a set of brake arms, one arm per brake pad, and pads on both the rear wheel and front wheel of the bicycle. The pads are manufactured of a semi-rigid rubberized material so as to frictionally grip the wheel when actuated. The brake pads are generally rectangular in shape, being long and narrow in order to provide sufficient surface contact against the normally narrow side of the wheel. The contact or braking surface of the pads typically include a variety of contours or tread patterns to increase frictional adhesion. Caliper brakes function as a vise by clamping against the wheels from both sides to compress the wheel between a pair or a set of brake pads. The compression and frictional contact of the brake pads slow or stop the rotation of the wheels and thus stop or slow the bicycle.
There are common problems associated with caliper brakes when they not adjusted properly, such as squealing, chatter, excessively rapid and uneven wear, and insufficient braking. The squealing, chatter, excessive uneven wear and/or insufficient braking results from improper contact of one or more of the brake pads with the side surface of the wheel. Such problems will even occur with the braking surface of the pad being parallel with the wheel when in the non-actuated or outward position. When the two surfaces (pad braking surface and wheel) are parallel when disengaged, and contact of the pads with the wheel is then made by squeezing the hand lever(s), the rearward end or toe of the pad tends to dig into the wheel first, being pulled slightly under and forward to a small degree by the rolling wheel, and this tends to angle the pad or pads to have the forward end or ends slightly outward away from the wheel, or to hold the front end of the pads off the wheel, typically resulting in pad squeal, chatter, reduced braking, an undesirable wear pattern or all of the above.
A prior art document, U.S. Pat. No. 4,768,623 issued Sep. 6, 1988 to M. Nagano, describes a bicycle cantilever caliper brake of a basic type in wide use today, and for the detailed drawings and description of the brakes and associated mechanical principles, this patent is herein incorporated by reference.
Another prior art document, U.S. Pat. No. 5,168,962 issued Dec. 8, 1992 to K. Yoshigai shows and describes cantilever and side pull caliper bicycle brakes, and for this information to general bike brake mechanics, this patent is herein incorporated by reference. The Yoshigai patent also describes the necessity of proper brake pad adjustment or clearance, further describing the problems associated with improper adjustment or clearance, and this information is another reason for the incorporation of the Yoshigai patent by reference.
Another relevant prior art document is U.S. Pat. No. 5,064,027 issued Nov. 12, 1991 to S. Akamatsu which teaches bicycle caliper brake pads having an extending member which abuts the wheel side surface to semi-automatically initially properly set or adjust the pads relative to the wheel, so that the pads have a small degree of toe-out. The Akamatsu patent also describes the necessity of proper brake pad adjustment or clearance relative to the wheel, and for this information, the Akamatsu patent is herein incorporated by reference.
Although the Yoshigai and Akamatsu patents each detail structuring and instructions for initially properly setting bicycle caliper brake pads relative to the adjacent wheel, it is known that the pads wear with use and can be pulled or slip out of alignment. This wear or misalignment can occur very quickly depending upon riding conditions, and the wear causes the pads to be slightly misshaped, rendering the pads out of proper adjustment and thus less effective at stopping or slowing the bicycle. The worn or out of alignment pads are not only less effective at stopping the bike, but also can make loud annoying noises when applied, such as squealing and chatter. Chatter is also associated with intermittent grabbing of the brakes and vibration.
Depending upon the degree of wear and/or misalignment of the pads, the pads can and should be readjusted periodically so as to set them in proper position relative to the wheel, and this may be necessary as often as once a day depending upon riding conditions. Such proper positioning is with the forward wheel contacting surface of the pads 2 to 4 millimeters nearer the wheel than the rearward end of the pad so that there is a small degree of toe-out, and this so that upon the pads being brought inward to contact the wheel, the front end contacts first, and this causes a small degree of deformation or angular pulling in the flexible pads which helps draw in or slightly pivot the rear end or toe of the pad so that under high clamping pressure, the pad braking surface is fully engaged with the wheel and generally parallel thereto. Improper adjustment such as insufficient toe-out can lead to the forward end of the pads gaping away from the wheel under high clamping pressures wherein only the rearward or toe end of the pads are left contacting the wheel. Alternatively, excessive toe-out can lead to the rear or toe end of the pads not contacting the wheel, and this of course reduces braking. The rear or rearward (toe) end of the pads is the end which the wheel rolls toward, and the front or forward end of the pads is the end which the wheel rolls away from when the bike is rolling forward.
Due to wear and/or misalignment of the pad surfaces which contact the wheel, bicyclist's who desire optimum performance from the brakes will periodically or whenever there are symptoms of wear or misalignment adjust the positioning of the pads so that the pads will be set with a small degree of toe-out, which is with the front ends of the pads 2 to 4 millimeters nearer the wheel side than the rear or toe end of the pads with the pads in the outward away from the wheel position (non-braking). This "toe-out" is only slight in appearance, being 2 to 4 millimeters, but does make a major difference in how the brakes perform. The proper toe-out may be as little as 1 millimeter and more than 4 millimeters depending upon the material flexibility and other characteristics of the pads and support arms. Most bicyclist's adjust the toe-out simply by eye, looking downward to define a slight gap by sight at the rearward end of the brake pad between the wheel side and braking surface of the pad. This procedure using sight is relatively inaccurate by nature, and often results is several trial and error attempts, and the process is normally further complicated by the pad position shifting slightly as the securing nuts and bolts on the brake arm are tightened to secure the pad in a fixed position. Additionally complicating the adjusting procedure is that both pads of a set, i.e., the left side pad and the right side pad should ideally have identical toe-out settings, as the two pads of a set function together to squeeze the wheel, and even pressure on each side of the wheel is ideal.
Additionally, it should be noted that not only should there be a slight amount of toe-out on properly set brake pads, but the elongated planar braking surface of the pads should be angularly tipped to match the typical slope of the wheel surface against which they abut, as normal bike wheels have a side surface which angles slightly inward, being further outward or wider at the major diameter of the wheel and sloping inward toward the wheel hub therefrom.